Police recorded the average speed of cars driving on a busy street by a school. For a sample of 25 speeds, it was determined that the average amount over the speed limit for the 25speeds was 12.8 mph with a standard deviation of 8 mph. The 90% confidence interval estimate for this sample is 10.06 mph to 15.54 mph.a) What is the margin of error for this problem?b) What size sample is needed to reduce the margin of error to no more than ±1?

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A First Course in Probability (10th Edition)

10th Edition

ISBN:9780134753119

Author:Sheldon Ross

Publisher:Sheldon Ross

Chapter1: Combinatorial Analysis

Section: Chapter Questions

Problem 1.1P: a. How many different 7-place license plates are possible if the first 2 places are for letters and...

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In a random sample of twelve people, the mean driving distance to work was 18.8 miles and the standard deviation was 4.9 miles. Assume the population is normally distributed and use the t-distribution to find the margin of error and construct a 90% confidence interval for the population mean μ. Interpret the results.
The police department estimated the average speed of cars along boul. St. Jean. With hidden radar, the speed of a random selection of 44 cars was measured. It yielded a sample mean of 53 km per/hr and a sample standard deviation of 5.9 km per/hr. What is the 99.9% confidence interval for the average speed of all cars driving on boul. St. Jean?
The sample mean and standard deviation for weights of 100 boxes are 12.05g and 0.1g respectively. Find a 90% confidence interval for the mean weight of the boxes.
An farmer is convinced that the weighing instrument for palay had a variability measured by standard deviation equal to 2. He recorded the measurements 4.1, 6.5, 5.2 and 10.2. Do these data confirm or disprove his assertion? Use a 95% confidence level.
In a random sample of 17 people, the mean commute time to work was 30.2 minutes and the standard deviation was 7.1 minutes. Assume the population is normally distributed and use a t- distribution to construct a 95% confidence interval for the population mean y. What is the margin of error of y? Interpret the results.
In a random sample of eleven people, the mean driving distance to work was 18.1 miles and the standard deviation was 7.6 miles. Assume the population is normally distributed and use the t-distribution to find the margin of error and construct a 99% confidence interval for the population mean μ. Interpret the results.
A wildlife study is designed to find the mean weight of salmon caught by an Alaskan fishing company. Find the minimum sample size needed in order to construct a 95% confidence interval for the mean weight of such salmon, to within 0.30 pounds. Assume that the standard deviation of 3.10.
In a sample of 100 individuals, the average height is 170 cm and the standard deviation is 15 cm. Using a 95% confidence level, what is the margin of error for the mean height of the population?
In a random sample of twelve people, the mean driving distance to work was 21.3 miles and the standard deviation was 7.3 miles. Assume the population is normally distributed and use the t-distribution to find the margin of error and construct a 99% confidence interval for the population mean μ. Interpret the results. Identify the margin of error. (Rol square miles miles per hour miles s needed.)
After a sewer spill into a lake, an environmentalist wanted to test to see if the water was safe (mean bacteria count per unit volume of water is less than 200). Ten samples along different locations of the lake resulted in a sample mean of 192.7 and a sample standard deviation of 10.81. 2. a. Construct a 95% confidence interval for the mean.
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